Event-related brain potentials and discrimination of steady-state vowels within and between phoneme categories: A preliminary study

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Abstract
The mismatch negativity (MMN), a component of the human auditory event-related brain potential, is elicited by a physically deviant stimulus in a sequence of homogeneo. “standard”, stimuli. MMN reflects an automatic discrimination process between the sensory input and the short-term memory trace left by the previous stimuli. These memory traces might form the neurophysiological basis of auditory sensory memory, the echoic memory. The purpose of the study was to determine whether the automatic discrimination process of vowels, as reflected in MMN, and the discrimination performance (measured as percentage of correct responses, d's, and RTs) with the same stimuli show effects of categorical perception. According to the results the study failed to show any statistically significant neurophysiological and behavioral effects of categorical perception on vowels. However, a consistent trend toward faster reaction times and better discrimination performance in phoneme boundary conditions than in phoneme center conditions was found. This trend was also reflected in MMN. The potential clinical value of the method described in the study is discussed.